RU2480631C1 - Vacuum centrifugal compressor - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: vacuum centrifugal compressor containing compression casing that is divided by partition to two sections, in the sections there are two rotors with impellers on common shaft that is mounted in casing on bearings. Note that the shaft has end seals, and sections have, at least, one inlet and discharge pipe branches and are connected by balancing line, according to the change, at least, one inlet pipe branch is located in the middle part of compression casing near partition, and supply pipe branches are located near end walls of compression casing, impellers of one section are located relatively the impellers of the other section by principle "face to face", and balancing line connects pressure cavities of sections. Invention task is to minimise buffer gas leakages into atmosphere and compressor.

EFFECT: reduction of centrifugal pump size, maintaining process gas concentration in compression casing.

Description

The invention relates to the field of centrifugal compressor engineering, in particular to vacuum circulation compressors.

In a number of technological processes of the closed cycle "compression-expansion" there is a need:

- maintaining a vacuum in the process gas circuit;

- preservation of the component composition (% concentration) of gas inside the circuit;

- minimize leakage of process gas into the atmosphere (up to complete tightness).

Known vacuum centrifugal compressor (hydrogen sulfide vacuum compressor 5GTs1-300 / 0,1-1,2 in the book of I.G.Hisameyev, V.A. Maksimov, G.S. Batkis, Ya.Z. Guzelbaeva "Design and operation of industrial of centrifugal compressors ”- Kazan: FEN Publishing House, 2010 on pages 615-623 with an initial pressure of 0.01 MPa abs. and a discharge pressure of 0.12 MPa abs.), containing a compression housing divided by a partition into two sections with sequential compression of gas and with intermediate gas cooling between sections located in sections two rotors with impellers on present a shaft mounted in the housing on bearings having end seals, the input and discharge pipes of each section. Arrangement of branch pipes consecutive (from a drive):

- input - discharge of the 1st section;

- input - discharge of the 2nd section.

To prevent the release of hydrogen sulfide gas from the compression housing or the suction of atmospheric air through the rotor seals, end seals are used with automatic maintenance of the set pressure of the gate gas (nitrogen) in the end seal chambers.

The disadvantages of the known vacuum centrifugal compressor is that in this compressor design it is necessary to use an unloading device (dumis) to reduce the axial loads on the thrust bearing, as well as the resulting dependence: the higher the pressure differential between the gate gas and the sealing process gas, the greater the leakage of the gate gas into the atmosphere and the more leakage of the gate gas into the flow part of the compressor. In a closed cycle, this dependence will lead to an increase in pressure in the process gas circuit and a change in the component composition of the gas.

At high volumetric flow rates of the process gas, which is typical for centrifugal compressors, a compressor design is used to reduce the diameter of the compressor, in which two sections work in parallel in a single housing.

The closest analogue of the proposed vacuum centrifugal compressor is a centrifugal compressor (VB Schnepp “Design and calculation of centrifugal compressor machines”, M., Mashinostroenie, 1995, on page 30), containing a compression housing, divided by a partition into two sections located in sections two rotors with impellers on a common shaft mounted in a bearing housing having end seals, the sections have at least one inlet and discharge nozzles and are connected by an equalization line. The impellers of one section are located relative to the impellers of another section according to the "back to back" scheme. The equalization line connects the suction sections. The inlet nozzles are located near the end walls of the compression housing, and the discharge nozzles are located in the middle of the compression housing near the partition.

This design of a vacuum centrifugal compressor allows you to:

1) minimize axial forces acting on the rotor from gas forces and dispense with the compressor design without an unloading device (dummis);

2) reduce the gate gas pressure, as compressor inlet pressure is sealed.

A disadvantage of the known design is that for vacuum centrifugal compressors, when the suction pressure is significantly lower than atmospheric (B), and the discharge pressure is slightly lower or slightly higher than atmospheric, this arrangement of the inlet and discharge nozzles leads to increased leakage of the gate gas into the atmosphere and (or) to increased leakage of buffer gas through the end seals into the flow part of the compressor, which is unacceptable in a number of technological processes.

The technical result of the invention is to minimize leakage of buffer gas into the atmosphere and the compressor.

The technical result is achieved by the fact that the vacuum centrifugal compressor containing the compression housing, which is divided by a partition into two sections, has two rotors with impellers on the common shaft, which is mounted on bearings in the housing, in the sections. The shaft has end seals, and the sections have at least one inlet and discharge nozzles and are connected by a surge line, according to the change, at least one inlet nozzle is located in the middle part of the compression housing near the partition, and the discharge nozzles are located near the end the walls of the compression housing, the impellers of one section are located relative to the impellers of the other section according to the “face to face” scheme, and the equalizing line connects the injection cavities of the sections.

Preferably, the vacuum centrifugal compressor comprises two inlet nozzles mounted on either side of the baffle, while preferably, the inlet and discharge nozzles of each section are connected by a pipe connecting the control valve.

The vacuum centrifugal compressor contains one inlet pipe, mounted in such a way that its outlet is divided by a partition into two parts.

It also preferably contains additional seals mounted on the shaft on both sides, separating the cavity of the sections from the end seals and bearings in the parking lot.

And the discharge pipes of the vacuum centrifugal compressor are preferably connected to one discharge pipe with a control valve, and the compression casing is designed for a discharge pressure (P _n ) close to atmospheric (B):

P _n = B + Δp, where

Δp = (0.001-0.1) V

The invention is illustrated by drawings, where:

- figure 1 schematically shows the proposed vacuum centrifugal compressor;

- figure 2 is the same with the pipeline connecting the inlet and discharge pipes of each section;

- figure 3 is the same, with one inlet pipe;

- figure 4 is the same with additional seals;

- figure 5 is the same with the discharge pipe connecting the discharge nozzles.

The vacuum centrifugal compressor (Fig. 1) contains a compression housing 1, which is divided by a partition 21 into two sections. In the sections are rotors 2 and 3 with impellers on a common shaft 4, which is mounted in the housing 1 on bearings 5 and 6 and has end seals 7. Each section has an inlet pipe 8 or 9 and a discharge pipe 10 or 11. Equalization line 12 connects cavity injection sections and thereby creates the same working conditions of the end seals. The inlet pipes 8 and 9 are located in the middle of the compression housing 1 near the partition 21, and the discharge pipes 10 and 11 are located near the end walls of the compression housing 1. The impellers of the rotor 2 of one section are located relative to the impellers of the rotor 3 of the other section according to the "face to face" scheme (figure 1).

This arrangement of nozzles and impellers has the following advantages:

1) the axial loads acting on the rotors 2, 3 from gas-dynamic forces are significantly reduced;

2) the required bearing capacity of the thrust bearings 5, 6 is reduced;

3) there is an opportunity to do without dummies in the compressor design;

4) the pressure of the buffer gas supplied to the chamber of the end seals 7 becomes close to atmospheric, since it is necessary to seal the discharge pressure, and not the suction pressure (as in the closest analogue), respectively, the leakage of the buffer gas into the flow part of the compressor and into the atmosphere;

5) in the case when, as a buffer gas, gas of the same composition as the process gas is supplied to the end seal chambers 7, the component composition of the gas in the circuit will be preserved.

The flowing parts of the sections cannot be completely identical, since they are made in a certain range of technological tolerances, therefore, to identify the gas-dynamic characteristics of parallel-running compression sections, it is proposed (Fig. 2) to connect the inlet 8, 9 and injection 10, 11 pipe sections to a pipe 14, which contains normally closed control valves 15, 16.

In a vacuum centrifugal compressor (Fig. 3), two inlet pipes 8, 9 can be combined into one inlet pipe 17, common to two sections, in order to simplify the design of the compressor and reduce its dimensions, as well as to eliminate gas-dynamic irregularities at the inlet.

In a vacuum centrifugal compressor (Fig. 4), to prevent air (gas) inflow from the environment, or buffer gas or oil vapors from the cavities of the end seals 7 and bearings 5, 6, into the flow part of the compressor during long-term parking, the vacuum centrifugal compressor contains additional seals 18 (Fig.4) mounted on the shaft 4 on both sides, separating the cavity of the sections from the end seals 7 and bearings 5, 6 in the parking lot. Before starting work after supplying the buffer gas to the cavity of the end seals 7, the seal 18 comes out of contact with the surface of the compressor rotors 2, 3.

In order to minimize leakage of buffer gas into the atmosphere and leakage into the flow part of the vacuum compressor (Fig. 5), the compression housing 1 is designed for a discharge pressure (P _n ) close to atmospheric (B)

P _n = B + Δp, where

Δp = (0.001 ÷ 0.1) B,

and discharge pipes 10, 11 are connected to one discharge pipe 19 with a control valve 20.

The proposed centrifugal vacuum compressor can operate as part of a compressor installation consisting of a compressor and a closed process gas circuit in which there is a process device where the discharge pressure is activated to the suction pressure. According to the technology, a limited increase in pressure may be allowed in the gas circuit due to the feeding of gate gas from the end seals, for example: not more than 0.3% per hour.

In this case, the compressor operates as follows. The process gas (with lower pressure) from the process circuit enters one (common to two sections) or two inlet pipes, is compressed in two parallel working sections and through two discharge pipes is discharged into the process gas circuit.

Claims (6)

1. A vacuum centrifugal compressor comprising a compression housing divided by a partition into two sections located in sections of two rotors with impellers on a common shaft mounted in a bearing housing having end seals, the sections have at least one inlet and discharge nozzles and connected by a surge line, characterized in that at least one inlet pipe is located in the middle part of the compression housing near the partition, and the discharge pipes are located near the end walls of the compression housing, the impellers of one section are located relative to the impellers of another section according to the “face to face” scheme, and the equalizing line connects the injection cavities of the sections. 2. The compressor according to claim 1, characterized in that it contains two inlet pipes mounted on opposite sides of the partition. 3. The compressor according to claim 2, characterized in that the inlet and discharge pipes of each section are connected by a pipe connecting the control valve. 4. The compressor according to claim 1, characterized in that it contains one inlet pipe, installed in such a way that its outlet is divided by a partition into two parts. 5. The compressor according to claim 1, characterized in that it contains additional seals mounted on the shaft on both sides, separating the cavity of the sections from the end seals and bearings in the parking lot. 6. The compressor according to claim 1, characterized in that the discharge nozzles are connected to one discharge pipe with a control valve, and the compression housing is designed for discharge pressure (P _n ) close to atmospheric (B):
P _n = B + Δp,
where Δp = (0.001-0.1) V.

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